The present invention relates to a composite for protection of objects, including the patient as well as surgical personnel, during laser surgery. In more detail, the present invention relates to a laser resistant composite for use in making objects such as surgical retractors, endotracheal tubes, catheters, and other items used in laser surgery for protecting both patient and surgical personnel from damaged tissue resulting from direct incidence of a laser on that object or reflected laser beams on tissue during surgery or from fire resulting from incidence of a laser on flammable materials.
Although most damage to the skin or other tissue from a laser is repairable, the extent of the damage varies depending upon the degree of absorption of the laser wavelength and the duration of exposure such that there is potential for serious damage. Adding to that potential is the fact that reflection of the laser beam is potentially as damaging as direct contact with the beam. Various safety measures are employed depending upon the surgical procedure to protect against such damage. For instance, a back drop is used behind the tissue being lased, when possible, and in the abdominal cavity, a wet wooden tongue blade, titanium rod or wet laparotomy sponge can be used to protect underlying tissue. Abdominal and cranial cavities are filled with sterile saline to absorb the energy of the beam. Non-involved, exposed tissue is covered with wet laparotomy sponges, four by fours, or cottonoids. Patients are restrained from movement, and beaded or other non-reflective instruments are used.
Fires can occur by ignition of a drape, endotracheal tube, or article of clothing, plastic, or rubber in the treatment area. On information and belief, none of the standard surgical drapes will resist impact from a laser beam. Precautions against fire include, for instance, the covering of surgical drapes with wet towels and/or laparotomy sponges, the wetting of all the drapes, sponges and gauzes used in the area of laser application, and the precautions listed above for protecting against laser burns. A more complete listing of these precautions is set out in the report of the Technical Practices Coordinating Committee of the Association of Operating Room Nurses, published as Recommended Practices--Laser Safety in the Practice Setting, 50 AORN J. 1015-1020 (November 1989) and in Safety Issues in Clinical Laser Management, published by Clinical Laser Monthly (February 1990).
A particularly dangerous fire problem is presented by the use of an endotracheal or nasotracheal tube for management of a patient during, for instance, an ENT procedure with a laser. To some extent, the problem exists with any procedure involving the use of a laser in the vicinity of a catheter or other disposable plastic or rubber surgical products, but in the case of an endotracheal tube, the tube is filled with pure oxygen such that the likelihood of fire is greatly increased. Polyvinyl chloride (PVC) and red rubber endotracheal tubes can melt upon exposure to laser beams, causing patient tissue burning, and metal and other flexible tubes can crack, causing fire when escaping oxygen ignites. Metal tubes are available which do not melt or burn, but they can block the surgeon's view, often are not as flexible as plastic or rubber tubes and may be larger in diameter thereby increasing the difficulty of inserting the tube, and can reflect the laser beam. In the case of large patients, the smaller internal diameter of flexible metal endotracheal tubes presents problems in providing adequate ventilation for the patient. It is known to wrap a rubber or PVC endotracheal tube with aluminum or other metal tape, but wrapped tubes are more difficult to insert, the ragged edges of the tape can damage the airway, the tape provides little protection against penetration of a laser beam, and the tape is laser reflective such that there is the posibility of damage or even fire from a reflected laser beam.
In short, the protection provided by even the most careful application of all of these precautions simply is not sufficient, and the precautions themselves give rise to certain inconveniences as listed. Depending upon the wavelength, time of exposure, type of laser and several other factors, the laser is capable of vaporizing these "protective" articles in exactly the same manner as the tissue on which the laser is intended to be used. There is, therefore, a need for a way to protect various objects such as surgical instruments, patients and surgical personnel in the treatment area.
Attempts have been made to provide an article which can be so used. U.S. Pat. No. 4,601,286 is directed to an "Article for the Protection of Living Tissues", said to protect" . . . living tissue from damage due to exposure to lasers . . .". That patent describes the use of a hydrogel in the form of a drape or dressing having an opening through which the laser light can pass to impinge on the portion of the tissue to be lased, the opening having a size and shape approximating that of the tissue site to be lased (col. 5, lines 13-20, 56-60). In practice, however, such an article does not protect against laser burns; at best, such articles may provide some protection against ignition because of the high water content of the hydrogel. Experimentation has shown that penetration of a twenty-five watt or greater laser through such articles is instantaneous; further, the hydrogels are clear, making them of limited use for argon lasers which "seek" color. Penetration of the laser through the hydrogel does not appear to depend on the thickness of the hydrogel--instead, the laser penetrates instantaneously no matter what the thickness.
Similarly, a laminate is available under the trademark MEROCEL LASER-GUARD from Americal Corporation (Mystic, Conn.) which is applied to an endotracheal tube, ostensibly for the purpose of protecting that endotracheal tube from damage by an incident laser beam. According to that company's promotional literature, that product is comprised of a 1 mm thick MEROCEL sponge portion which, on information and belief, is a hydrogel composed of a polyvinyl alcohol, and a 1 mil metal foil laminated to each other by "a special waterproof hypoallergenic adhesive". Although the promotional literature for that product indicates that the laminate is capable of withstanding incident laser beams for up to 90 seconds, experimentation has shown that such claims may be somewhat optimistic. Further, that product, when applied to rubber or some PVC endotracheal tubes, decreases the flexibility of the endotracheal tube because it is supplied as a long rectangular patch into which the tube portion of the endotracheal tube is rolled. As noted above, the flexibility of the tube is important because stiffer tubes are more difficult to insert.
There is, therefore, still a need for a material which can be applied to an object such as an endotracheal tube to provide effective protection from an incident laser beam. There is also a need to which the two approaches summarized have not even attempted to respond, namely, the need for protecting objects such as retractor blades, endoscopes, specula, and other objects used during laser surgical procedures from damage by exposure to the laser beam, and to protect living objects (the patient and surgical personnel) from reflected laser beams.